Orexin is a neuropeptide locally produced in the lateral hypothalamus, and orexin A and orexin B which consist of 33 or 28 amino acids, respectively, are now identified. Both orexin A and orexin B are endogenous ligands of the orexin receptors, which are G protein-coupled receptors mainly present in the brain, and two types of subtypes, type 1 and type 2, are known for the orexin receptors (non-patent document 1).
Since orexin is localized in feeding center, and intraventricular administration thereof results in an increase in food intake, orexin initially attracted attention as a neuropeptide having a feeding behavioral regulation. Thereafter, however, it was reported that the cause of dog narcolepsy is genetic mutation of orexin type 2 receptor (non-patent document 2), and the role of orexin in sleep-wake controlling has been also attracted.
From the studies using a double transgenic mouse obtained by crossing orexin neuron-deficient transgenic mouse with orexin overexpressing transgenic mouse, it is considered that monoaminergic nerve and cholinergic nerve are activated by orexin during wakefulness, and thereby the balance between sleep and wakefulness is shifted toward wakefulness phase to maintain wakefulness state, and on the other hand, orexin nerve is suppressed during sleep, and thereby sleep phase is maintained (non-patent document 3). In addition, it was reported that administration of a compound having same level antagonistic activities against orexin type 1 and orexin type 2 receptors decreases activity, shortens sleep latency, and increases total sleep (non-patent document 4 and non-patent document 5).
Therefore, a compound having an orexin receptor antagonistic activity is expected to exhibit sleep-promoting action, and to be useful as an novel agent for the prophylaxis or treatment of sleep disorder. As a compound having an orexin receptor antagonistic activity, for example, compounds having various structures, which are described as a review article in non-patent documents 6-8, are known. In addition, patent documents 1 to 6 describe homopiperazine derivatives and the like. However, these documents do not describe the 1,2,5-oxadiazepane ring compound described in the present specification.
Patent Document 1 describes the following compound, which has an orexin receptor antagonistic activity, and is useful for the prophylaxis or treatment of sleep disorder, insomnia and the like.
wherein each symbol is as defined in the document.
Patent Document 2 describes the following compound, which has an orexin receptor antagonistic activity, and is useful for the prophylaxis or treatment of sleep disorder, depression, anxiety, cognitive disorder, appetite disorder, addiction disorder and the like.
wherein each symbol is as defined in the document.
Patent Document 3 describes the following compound, which has an orexin receptor antagonistic activity, and is useful for the treatment of insomnia, jet-lag, depression, schizophrenia, obesity and the like.

Patent Document 4 describes the following compound, which has an orexin receptor antagonistic activity, and is useful for the treatment of sleep disorder, insomnia and the like.
wherein each symbol is as defined in the document.
Patent Document 5 describes the following compound, which has an orexin receptor antagonistic activity, and is useful for the treatment of sleep disorder, insomnia and the like.
wherein each symbol is as defined in the document.
Patent Document 6 describes the following compound, which has an orexin receptor antagonistic activity, and is useful for the treatment of sleep disorder, insomnia and the like.
wherein each symbol is as defined in the document.